cc: Async readback.

cc/resources/resource_provider.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/resources/resource_provider.h"
 
 #include <limits.h>
 
 #include "base/debug/alias.h"
 #include "base/hash_tables.h"
@@ skipping 438 matching lines @@
 
   context3d->shallowFlushCHROMIUM();
   return true;
 }
 
 const ResourceProvider::Resource* ResourceProvider::LockForRead(ResourceId id) {
   DCHECK(thread_checker_.CalledOnValidThread());
   ResourceMap::iterator it = resources_.find(id);
   CHECK(it != resources_.end());
   Resource* resource = &it->second;
-  DCHECK(!resource->locked_for_write || resource->set_pixels_completion_forced);
+  DCHECK(!resource->locked_for_write ||
+         resource->set_pixels_completion_forced) <<
+      "locked for write: " << resource->locked_for_write <<
+      " pixels completion forced: " << resource->set_pixels_completion_forced;
   DCHECK(!resource->exported);
   // Uninitialized! Call SetPixels or LockForWrite first.
   DCHECK(resource->allocated);
 
   if (!resource->gl_id && resource->external && !resource->mailbox.IsEmpty()) {
     WebGraphicsContext3D* context3d = output_surface_->context3d();
     DCHECK(context3d);
     if (resource->mailbox.sync_point()) {
       GLC(context3d, context3d->waitSyncPoint(resource->mailbox.sync_point()));
       resource->mailbox.ResetSyncPoint();
@@ skipping 751 matching lines @@
 void ResourceProvider::EnableReadLockFences(ResourceProvider::ResourceId id,
                                             bool enable) {
   DCHECK(thread_checker_.CalledOnValidThread());
   ResourceMap::iterator it = resources_.find(id);
   CHECK(it != resources_.end());
   Resource* resource = &it->second;
   resource->enable_read_lock_fences = enable;
 }
 
 }  // namespace cc